The introduction of SANS 10400-XA regulations relating to energy usage in buildings, as part of the wider code of practice, gives substance to South Africa’s national building regulations as far as energy efficiency within a building is concerned.

Words Submitted by Scott Quarmby (Thermguard) – compiled by Gareth Griffiths

Energy performance
of buildings and the role of insulation

Improved energy efficiency within a building means less use of fossil-fuel based energy used in heating and cooling, leading to a reduction in greenhouse gas production, an objective of the regulations.

Energy performance of buildings

Recently, the provisions of the National Energy Act were invoked, requiring the implementation and display of energy performance certificates in terms of SANS 1544:2014 in certain categories of buildings. This is expected to drive the design and management of buildings towards lower energy consumption. Hence, any move towards increased energy efficiency within buildings is seen as a positive.

South Africa has also experienced an immense increase in the cost of all forms of fossil fuel-based energy – providing a significant financial incentive for specifiers and owners to move to greater energy efficiency in all buildings, including domestic dwellings.

The effect of SANS10400-XA

The SANS10400-XA standard specifies minimum thermal resistance values (R-Values) to be achieved inside the roof of a building, depending on the SA Climatic Zone (per SANS 204) in which the building is located. The effect of this standard has been far-reaching, even with developers of low-cost housing or a homeowner or contractor renovating an existing building having to comply.

Bulk insulation products such as cellulose fibre insulation offer an effective way of complying with the R-Value requirements, mandatory in all new property developments or refurbishments. The products lend themselves to retrofitting.

Retrofitting typically occurs where a homeowner (or office property owner) becomes concerned about a rising energy bill, or power blackouts (load shedding) meaning no climate control indoors; or by the ongoing discomfort of the occupants of a building caused by seasonal temperature extremes. Discomfort inside a building causes a loss in worker productivity, sick building syndrome or unhealthy living conditions, if in a home.

Gareth Griffiths

Graph shows the temperature profile within the roof space over a 24-hour period – the first probe being placed immediately below the roof tiles and the second probe on top of the ceiling board or below the insulation layer when present. The red border indicates the period of maximum summertime heat – 10:00 – 16:00.

The graph displays the set of results in the insulated scenario where the ambient temperatures were similar for a 24-hour period. Note at peak period of heat, a differential of at least 2°C was observed between the two materials. The red border indicates the period of maximum summertime heat – 10:00 – 16:00.

In situ empirical tests

Cellulose fibre insulation manufacturer, Thermguard, supplier of both the Eco-Insulation and Thermguard brands, recently undertook testing under real-life conditions to back up the generic deemed to comply methodology on which R-Values are described in SANS204:2011.

Testing began in summertime, mid-November 2019, ending in February 2020 in an average-sized family home on the highveld. Climatic Zone 2 (as per SANS 204:2011) applies.

Temperature probes were placed in standardised positions throughout a typical 3-bedroom home which was fitted with generic bulk blanket insulation. Real time temperature data was recorded on a data logger throughout the day for a period of four weeks. The blanket insulation was then removed, and recordings were taken for a further week to provide a baseline with no insulation. Finally, the house was fitted with Thermguard cellulose fibre insulation and temperature recordings were taken for a period of eight weeks. In both insulated scenarios, insulation was installed on the minimum deemed-to-satisfy thicknesses for Zone 2 (115mm thickness).

Under the guidance of an actuary, the three test scenarios were evaluated using an ‘insulation score’. The score quantifies how well the insulation performs in regulating the internal temperature of the home. Prevailing outdoor climatic conditions had also been monitored to ensure an even comparison on days regarded as having similar weather.

As expected, the presence of insulation above the roof led to a much smoother variation in temperature through the day – lower highs and higher lows. The test results provide useful insight to interpreting the actual performance of insulation as opposed to the SANS204 deemed to comply methodology.

Significantly, the unaudited comment of the analyst is that the test analysis shows that at a 99% confidence level the cellulose fibre insulation employed is a better insulator than the generic blanket insulation and that both types are significantly better than no insulation at all.

The unaudited conclusions of the independent analyst were that cellulose fibre was 6.8 times more effective than no insulation, while the generic blanket insulation was 2.8 times more effective than no insulation. Although both types of insulation complied with the deemed to comply requirements of SANS204:2011, cellulose fibre was 2.4 times more effective as an insulator compared to the insulation blanket material.

The tests pointed to cellulose fibre being a superior insulation material, even when R-Values are the same. This brings into question the reliance on R-Value as the only factor when considering insulation thermal performance. Potentially, another factor to consider is the more efficient method of application of cellulose fibre into the ceiling where it flows under pneumatic pressure into every nook and cranny, creating a seamless fill above the ceiling.